Conventional hot water heating apparatuses are shown in U.S. Pat. No. 3,247,940 to Christine, et al., and U.S. Pat. No. 3,884,389 to Martin. Each apparatus includes a larger lower chamber having a heating element provided in the bottom thereof for heating the water therein prior to discharge; the Martin patent structure aiding the efficiency by having the cold water duct within the hot water chamber and with controls such that the heater is energized to begin heating in response to the temperature of the inflowing cool water.
Although these conventional heaters are of sufficient efficiency to provide water of sufficient high temperatures for vending purposes, the number of vends or the quantity of hot water immediately available without the temperature thereof reduced, is restricted; for example, to approximately twenty cups of coffee.